Many methods and devices have been proposed to force open safety deposit boxes. Some of them have met with mitigated success. Few methods in use today are described below.
One of these methods is named "punching the lock". It involves a punching of the lock with a steel punch. This method invariably causes severe damage to the tray placed inside the safety box. Sometimes, the hinges are damaged beyond repairs and the back rest of the door is damaged during the operation.
Another one implies a picking of the lock. This method can only be used by a trained technician or experienced locksmith. A small hole is drilled in the door immediately above the keyhole and, by the use of a false key and a small diameter steel rod, the fingers of the lock are aligned to open it. It is mostly used where the lock must be saved. Afterward, the hole must be plugged and door surfaces re-finished before re-utilization.
Another method implies a drilling of the three holding screws of the lock by using a template to locate the screws. Afterward, extensive door repairs and lock replacement are needed.
The lock can also be pulled. A thin split steel blade is inserted in the keyhole, and it expands when pulling pressure is applied. The action of the steel blade is similar to that of a fish hook. The pressure is applied via an eye at the outer end of the blade by means of shaped brackets or levers. The drawbacks of this method is that, against the sturdier types of locks, the blade will break or cut through the brass cylinder of the lock and come out leaving the door locked. Sometimes, the cylinder is pulled out from the lock, leaving the door locked.
A popular method used by technicians is to drill a hole in the cylinder of the lock, thread this hole using a tap and screw a bolt of the proper size into this threaded hole. Then, using a lever and fulcrum, apply outward pressure on the bolt until door opens. Should the cylinder come out, a steel hook is inserted in the hole to replace the bolt. The drawbacks with this method are that the length of the lever required, which length is from 2 to 3 feet, makes it ackward and sometimes impossible to use it in a confined space. A user may hurt himself as the pressure required to break the lock is supplied by the user's hands pushing against the lever. Sometimes, the hinges are damaged because of the type of pressure applied. This method does not work on doors having a length of 10".